In a diallel cross of Phaseolus aureus involving five varieties, combining ability and gene action for grain yield, grains per pod and pods per plant were estimated. The study indicated that both general combining ability and specific combining ability effects were significant and important for all three traits. Partial dominance for grain yield and partial to over-dominance for grains per pod and pods per plant were observed. Dominant genes seem to govern the inheritance of all three characters. Combining ability, and graphical and component variance analyses indicated that the grain yield and two of its components are influenced by both additive and non-additive gene action.